There is currently considerable interest in both improving academic achievement (No Child Left Behind) and reducing the rates of obesity and its associated negative health consequences in elementary school students. Increased physical activity (PA) offers a potential intervention to address both issues. To provide increased PA while maintaining academic instruction time, we developed a program we call Physical Activity Across the Curriculum (PAAC) in which regular classroom teachers were trained to deliver academic lessons using moderate to vigorous physical activity (MVPA) for 20 minutes/d, 5 days/wk. We evaluated PAAC in a 3-year cluster randomized trial (DK61498) with the primary aim of preventing increases in obesity in students in grades 2 and 3 at baseline. Results from PAAC indicated a significant reduction (p =0.02) in the increase in BMI for students attending schools receiving 75 minutes or greater of PAAC compared to control. We also evaluated academic achievement (Weschler Individual Achievement Test- Second Edition WIAT-II) in a randomly selected sub-sample at baseline and at year 3. Although sub-sample analyses were inadequately powered, both the composite academic achievement score, and specific scores for reading, math, and spelling improved significantly in students receiving PAAC compared with control. Based on our results from PAAC we are proposing an adequately powered, 3 year, cluster randomized trial (A+PAAC) with the primary aim of assessing the impact of academic lessons taught through PA on the academic achievement of elementary school students (n = 210 intervention, n= 210 control) in grades 2 and 3 at baseline. Fourteen schools will be randomized to receive either A+PAAC lessons, or regular sedentary lessons (control). We expect students in elementary schools that receive A+PAAC lessons will have significantly greater increases in academic achievement from baseline to 3 years compared to CON. In addition, we propose to evaluate potential mediators of any association between change in PA and change in academic achievement. Potential mediators include cognitive function, BMI, cardiovascular fitness, attention to task, and daily PA.